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Coronary Heart Disease/Coronary Artery Disease (CAD)/Ischemic Heart Disease/Coronary Atherosclerosis
Published in Charles Theisler, Adjuvant Medical Care, 2023
Coronary arteries are the blood vessels that deliver oxygenated blood to the heart. Coronary atherosclerosis, also commonly known as coronary artery disease and coronary heart disease, is a > 50% narrowing of any coronary artery. When cholesterol, fat, and calcium plaque builds up and hardens within the innermost layer (intima) of the coronary arteries, the wall becomes thicker and more stiff. This reduces or blocks the flow of rich oxygenated blood that can reach the heart. The resulting myocardial ischemia can lead to shortness of breath, palpitations, chest pain (angina), heart attack, arrhythmias, and heart failure.
Specialized Circulations in Susceptible Tissues
Published in Wilmer W Nichols, Michael F O'Rourke, Elazer R Edelman, Charalambos Vlachopoulos, McDonald's Blood Flow in Arteries, 2022
Myocardial ischemia (insufficient blood supply to the myocardium) results when there is an imbalance between supply and demand, with blood supply insufficient to meet demand. This may result from increased demand, as when heart rate and systolic pressure increase during exercise (Duncker and Bache, 2008), or when supply is limited by coronary narrowing, “endothelial dysfunction” or decreased coronary perfusion time. If severe and prolonged, ischemia results in irreversible myocardial damage (myocardial infarction). The classic symptom of myocardial ischemia is oppressive chest pain or discomfort and is termed “angina pectoris”; myocardial ischemia, however, may occur without symptomatic angina.
Myocardial Perfusion Imaging
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Elin Trägårdh, David Minarik, Mark Lubberink
Myocardial ischemia occurs when the supply of oxygen to the myocytes is lower than the demand (Figure 15.1). The inotropic and chronotrophic states determine the myocardial demand. For example, during physical exercise, the increasing heart rate and blood pressure lead to an increased demand for oxygen. In normal conditions, the arterioles can dilate during exercise, and perfusion can increase from a resting value of 1 mL/min/g tissue to more than 3 mL/min/g. IHD is often caused by atherosclerotic stenosis in the coronary arteries, which increase the resistance in the vessels and limits the blood flow. The heart will compensate for this at rest by dilation of the arterioles, thereby preventing a flow decrease. This, however, means that part of the flow vasodilator reserve is already being used at rest, and the arterioles cannot dilate further during stress. Thus, there is a lower supply of oxygen to the myocytes at stress, but not at rest, which is why patients who have stress-induced ischemia often have normal perfusion at rest.
Blocking RIPK2 Function Alleviates Myocardial Ischemia/Reperfusion Injury by Regulating the AKT and NF-κB Pathways
Published in Immunological Investigations, 2023
MI/R injury is linked to multiple pathological factors, including endothelial dysfunction, metabolic disorders, oxidative stress, mitochondrial damage, neutrophil infiltration, apoptosis, inflammatory response, autophagy et.al. Among them, apoptosis, inflammation, and oxidative stress are all important in the pathogenesis of myocardial ischemia (Rios-Navarro et al. 2019). MI/R injury can trigger cell apoptosis and enhance infarct area, which is a crucial factor that affects the treatment of acute myocardial infarction (Rios-Navarro et al. 2019). When MI/R occurs, it immediately triggers an inflammatory response that persists throughout the reperfusion process (Lee et al. 2019), followed by the release of inflammatory cytokines. Inflammatory factors, such as TNF-α and IL-1β, not only contribute to inflammation, but also promote the production of oxygen free radicals, increasing oxidative stress in myocardial tissues and exacerbating myocardial tissue injury (Besch et al. 2018). However, many traditional antioxidants have not demonstrated significant efficacy (Bae et al. 2016). Thus, reducing apoptosis, inflammatory response, and oxidative stress in myocardial tissues during I/R is the key factor in preventing MI/R.
A Statewide Assessment of Prehospital Electrocardiography Approaches of Acquisition and Interpretation for ST-Elevation Myocardial Infarction Based on Emergency Medical Services Characteristics
Published in Prehospital Emergency Care, 2020
Jessica K. Zègre-Hemsey, Mehul D. Patel, Antonio R. Fernandez, Michele M. Pelter, Jane Brice, Wayne Rosamond
EMS providers acquired additional prehospital ECGs when the initial ECG was non-diagnostic if the patient experienced ongoing symptoms and/or had a change in clinical status. These results are important based on the premise that acute myocardial ischemia is dynamic; therefore, a single snapshot ECG may not always capture acute ST-segment changes. The standard ECG has limited sensitivity (30%–70%) and specificity (70%–95%) that results in 2–5% of patients with ACS being erroneously discharged from the ED, and 70% of patients being admitted for suspicious ACS not having it (12). In a previous study, the sensitivity significantly increased to nearly 80% when both a prehospital ECG and the initial hospital ECG acquired in the ED were considered (13). Findings underscore the importance of serial ECG monitoring to improve both rapid and accurate diagnosis of acute myocardial ischemia.
Characteristics of Prehospital Electrocardiogram Use in North Carolina Using a Novel Linkage of Emergency Medical Services and Emergency Department Data
Published in Prehospital Emergency Care, 2019
Jessica K. Zègre-Hemsey, Josephine Asafu-Adjei, Antonio Fernandez, Jane Brice
Rapid and accurate identification of acute coronary syndrome (ACS) is critical for reducing patient morbidity and mortality and optimizing outcomes (1). The electrocardiogram (ECG) is the most widely used diagnostic test to determine acute myocardial ischemia and/or infarction and is inexpensive, noninvasive, and readily available. Mounting evidence suggests that prehospital ECG results are significantly associated with ACS diagnoses, fewer adverse clinical events, less total ischemic burden time, and long-term survival (2–5). Prehospital ECG findings of myocardial ischemia direct the next steps for emergency medical service (EMS) personnel, such as bypassing the nearest hospital for one farther away offering percutaneous coronary intervention (6). Prehospital ECG use is associated with decreased time to treatment, increased activation of the cardiac catheterization laboratory, and improved diagnostic accuracy of ACS when used in conjunction with the initial hospital ECG acquired in the emergency department (ED) (4, 5). Despite these benefits, prehospital ECG use for chest pain patients varies [20–80%] due to differing levels of prehospital care, lack of standardized protocols, data collection procedures, and differences in EMS personnel training (7–9).